1. Field of the Invention
This invention relates to diacetylenic monomers and polymers and, more particularly, to carbazolyl diacetylene and its derivatives, useful as photoconductive and non-linear optical materials and as high energy radiation dosage indicators.
2. Description of the Prior Art
In the development of photoreceptors for use in commercial imaging systems such as electrophotography, the importance of organic polymer materials has rapidly increased due to cost considerations and the wide range of obtainable properties. Consequently, there has been recent interest in the photoelectronic properties of organic polymers. For practical use over a wide range of operational conditions, the materials must be able to form a film having a large area, have a high resolution of the image and maintain mechanical integrity. It has long been recognized that among many organic solids, amorphous poly-N-vinyl-carbazole (PVK), in which the carbazolyl groups are attached to a carbon-carbon single bond polymer backbone, is an important photoconductor. At the present time, PVK has been successfully utilized as a material for electrophotography. However, while this material is very useful, new materials having even more exceptional properties are required to further increase the efficiency of imaging systems.
Frequency tripling (or doubling) using non-linear optical devices is important in order to obtain high power laser sources in frequency ranges such as the ultraviolet and near-infrared where conventional high power laser sources are unavailable. Certain polydiacetylenes have been shown to have the highest third order susceptibilities (X.sup.(3)) known for materials with a comparable transparency range in the near-infrared; see Vol. 36, Physical Review Letters, pp. 956-959 (1976). These third order susceptibilities are comparable in magnitude to those found for germanium. However, germanium is not usable at wavelengths below 2 .mu.m, while the polydiacetylenes are usable down to about 0.6 .mu.m. Compositions possessing even higher third order susceptibilities usable at such short wavelengths are desired.
Since high energy irradiation has become an economically viable means of sterilization, reliable radiation dosage indicators are required. Many diacetylenes are known to react upon exposure to gamma ray irradiation, that is, they undergo a color change indicating polymerization. However, the response is usually gradually developed and an instrument (e.g., a spectrophotometer) is generally required for determining dosage. Compositions capable of sharp, visual indication at some threshold dosage of radiation are desired.